fix: update stopped working with banner

With the addition of `--banner` option index files no longer start with '// @create-index'

This new regex looks for '// @create-index' that are either at the beginning of the file (old behavior) or if it is followed by a newline.
Basically it just checks whether it exists in a file or not.

Added a test for it now.

src/utilities/validateTargetDirectory.js

@@ -1,6 +1,5 @@
 import fs from 'fs';
 import path from 'path';
-import _ from 'lodash';
 
 export default (targetDirectory) => {
   let stats;
@@ -25,7 +24,7 @@ export default (targetDirectory) => {
 
   const indexFile = fs.readFileSync(indexFilePath, 'utf8');
 
-  if (!_.startsWith(indexFile, '// @create-index\n')) {
+  if (!indexFile.match(/(?:^|[\n\r]+)\/\/ @create-index[\n\r]+/)) {
     throw new Error('"' + indexFilePath + '" unsafe index.');
   }
 

test/fixtures/validate-target-directory/safe-index-with-banner/index.js

@@ -0,0 +1,3 @@
+/* eslint-disable */
+
+// @create-index

test/validateTargetDirectory.js

@@ -36,6 +36,11 @@ describe('validateTargetDirectory()', () => {
         expect(validateTargetDirectory(path.resolve(fixturesPath, 'safe-index'))).to.equal(true);
       });
     });
+    context('safe with banner', () => {
+      it('returns true', () => {
+        expect(validateTargetDirectory(path.resolve(fixturesPath, 'safe-index-with-banner'))).to.equal(true);
+      });
+    });
     context('unsafe', () => {
       it('throws an error', () => {
         expect(() => {